1. Field of the Invention
This invention relates generally to a method and apparatus for electrical stimulation of the esophagus. More particularly, this invention relates to a method and apparatus for electrical stimulation of a portion of the esophagus including the lower esophageal sphincter so as to reduce acid reflux.
2. Description of the Prior Art
As is generally known to those skilled in the art, gastro-esophageal reflux disease (GERD) is a common chronic condition affecting more than 10% of the population in the United States. GERD is associated with significant morbidity and impaired quality of life. This condition results from exposure of esophageal mucosa to gastric acid as the acid refluxes from the stomach into the esophagus. The acid damages the esophageal mucosa resulting in heartburn, ulcers, bleeding, scarring, Barrett's esophagus (pre-cancerous esophageal lining) and adeno-cancer of the esophagus. The incidence of GERD in the United States has risen two to three folds over the last decade.
In the prior art heretofore, acid suppression with medications (H-2 receptor antagonists or proton pump inhibitors) is the mainstay of therapy. Alternatively, open surgical or laparoscopic fundoplication is used in a few patients. However, these procedures all suffer from the disadvantages that they are associated with significant morbidity and small but finite mortality. More recently, there has been an interest which is focused on endoscopic treatments of GERD.
As used herein, the lower esophageal sphincter (LES) is a smooth muscle located between the stomach and the esophagus which acts as a barrier to gastric acid reflux. Transient lower esophageal sphincter relaxation (TLESR) is the major pathogenic mechanism for GERD. Decreased LES tone may also cause or contribute to GERD. Therefore, it would be desirable to prevent relaxation of the LES and/or increase LES tone in order to increase the barrier action of the LES, thereby reducing the exposure of esophageal mucosa to gastric acid reflux. Most of the newer endoscopic techniques of the prior art rely on inducing scarring and/or hypertrophy of LES to reduce or prevent relaxation of the LES by producing injury using radio frequency or thermal ablation. Other prior art procedures have tried to alter the LES by placing mucosal sutures or submucosal injection of silicone in the LES. However, all of these prior art methods suffer from the major disadvantage in that they induce injury. Further, the results are substantially irreversible, and there is limited ability to make adjustments without requiring subsequent endoscopic procedures.
It is also generally known in the art that smooth muscles and associated nerves can be electrically stimulated so as to cause the muscle to contract or relax. For example, it is known in the art to electrically stimulate the heart with an implanted pacemaker for creating contractions at a rate compatible with providing adequate blood supply to the heart. It is further known in the art to artificially propagate contractions of the gastro-intestinal (Gl) tract by implanting electrodes below the LES to facilitate emptying portions of the tract. This latter method uses electrode sets which are placed serially along the Gl tract so as to successively and repetitively stimulate contractions, thereby propagating contents through the tract portion.